Design and Performance Provisions - City of Norwalk

CITY OFNORWALK 

SewerStandardPlans 

andDesignStandards 

forSewerFacilities

CITY OF NORWALK 

SEWER STANDARD PLANS 

AND 

DESIGN STANDARDS FOR SEWER FACILITIES 

Prepared By: 

AKM CONSULTING ENGINEERS 

553 Wald 

Irvine, California 92618 

(949) 753-7333 

Prepared For: 


12700 Norwalk Boulevard 

Norwalk, California 90650 

(562) 929-5723 

APRIL 2009


DESIGN STANDARDS FOR SEWER FACILITIES 

SECTION 3 

TABLE OF CONTENTS 

Section 

1 Standard Requirements ...................................................................................................1 

2 Calculations Required......................................................................................................1 

3 Size....................................................................................................................................1 

4 Minimum and Maximum Slope ........................................................................................2 

5 Design Flow Criteria.........................................................................................................2 

6 Standard Location and Alignment .................................................................................3 

7 Easements ........................................................................................................................4 

8 Horizontal Curves.............................................................................................................4 

9 Stationing Procedure .......................................................................................................4 

10 Minimum Depth ................................................................................................................4 

11 Sewer Pipe Material..........................................................................................................4 

12 Manholes...........................................................................................................................5 

12.1 Manhole Requirements...........................................................................................5 

12.2 Manhole Type and Size ..........................................................................................5 

12.3 Manhole Covers......................................................................................................5 

12.4 Manhole Linings and Coatings................................................................................6 

12.5 Manhole Warning Signs..........................................................................................6 

13 Clean-Outs ........................................................................................................................7 

14 Separation Between Sewer and Water and Recycled Water Lines...............................7 

15 House Laterals..................................................................................................................7 

16 Private Sewer System ......................................................................................................8 

17 Sewer Pump Station.........................................................................................................8 

17.1 General...................................................................................................................8 

17.2 Standards and Codes .............................................................................................9 

17.3 Design Flows and Heads ........................................................................................9 

17.4 Drivers ..................................................................................................................10 

17.5 Wet Well...............................................................................................................10 

17.6 Emergency Storage ..............................................................................................11 

17.7 Dry Well................................................................................................................12 

17.8 Standby Equipment...............................................................................................12 

17.9 Pumps ..................................................................................................................13 

17.10 Valves and Gates .................................................................................................15 

17.11 Magnetic Flow Meters...........................................................................................19 

17.12 Piping and Support System...................................................................................20 

17.13 Ancillary Equipment ..............................................................................................22 

Page 

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DESIGN STANDARDS FOR SEWER FACILITIES

TABLE OF CONTENTS 

(Continued) 

17.14 Electrical Equipment .............................................................................................29 

17.15 Instrumentation and Controls................................................................................29 

17.16 Supervisory Control and Data Acquisition (SCADA) System.................................33 

17.17 Pressure Gauges..................................................................................................33 

17.18 Pump Station Facility ............................................................................................34 

17.19 Force Mains..........................................................................................................34 

17.20 Access Roads.......................................................................................................35 

17.21 Flood Control ........................................................................................................35 

17.22 Grading and Area Drainage ..................................................................................35 

17.23 Soils Report ..........................................................................................................35 

17.24 Surveying..............................................................................................................35 

17.25 Security.................................................................................................................36 

17.26 Water Supply System ...........................................................................................36 

17.27 Landscaping and Irrigation System.......................................................................36 

17.28 Construction..........................................................................................................36 

18 Inspection and Testing of Gravity Sewers ...................................................................37 

18.01 CCTV Inspection...................................................................................................37 

18.02 Gravity Pipe Leakage Tests..................................................................................38 

18.03 Manhole Leakage Tests........................................................................................38 

18.04 Pipe Slope ............................................................................................................39 

19 Standard Sewer Notes ...................................................................................................39 

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1. STANDARD REQUIREMENTS 

The design and construction of all sanitary sewer system facilities to be operated and 

maintained by the City of Norwalk (City) shall be in accordance with these Design Criteria, 

and the latest edition of the following: 

 

 

 

 

 

 

 

The City of Norwalk Standard Plans, latest edition 

Standard Specifications for Public Works Construction (Greenbook), 

City of Norwalk Sewer System Management Plan, 

Statewide General Waste Discharge Requirements issued by the State Water 

Resources Control Board (Order No. 2006-0003) 

Requirements of the jurisdictional agencies where the work shall be performed 

Cal-OSHA requirements 

Los Angeles County Code 

2. CALCULATIONS REQUIRED 

3. SIZE 

Substantiating engineering calculations for design flows; pipe size; pump, motor, generator, 

wet well size and appurtenant equipment selection; structural design, and bedding/backfill 

designs shall accompany plan submittals to the City. All calculations shall be sealed and 

signed by a California registered professional engineer. 

Where flow from a new development or redevelopment is added to an existing sewer, and 

where the new development or redevelopment is in an area of questionable sewer capacity, 

the existing sewer shall be flow monitored by a qualified company acceptable to City at the 

owner’s cost for a minimum period of two weeks to verify the existing minimum, average, 

and peak dry weather flows. Two copies of the report shall be submitted to City in the City’s 

required format. The City will determine the adequacy of capacity in all the facilities that will 

convey the subject flow. 

Gravity Sewers 

The minimum size gravity sewer shall be 8-inches in diameter. The City of Norwalk may 

accept 6-inch diameter sewer lines if they must be used to provide adequate velocity. 

Sewer pipes shall not be constructed in a common trench with another utility. Adequate 

horizontal and vertical clearance shall be maintained in accordance with the State of 

California Department of Health Services “Criteria for the Separation of Water Mains and 

Sanitary Sewers”. 

Force Mains 

The size of sewer force mains shall be determined during the design phase of the project 

based upon a comparative study of the construction cost and pumping costs for several 

alternative sizes. In no case shall a force main be less than 4 inches in diameter. The 

capacity of the force main shall be the design peak flow from the pump station. The 

minimum design velocity for a force main shall be 3.0 fps, and maximum allowed 5.0 fps. 

The discharge shall be into a manhole with a smooth flow transition to a gravity sewer. The 

force main terminal manhole shall be PVC lined. 

R:\RPTS\Norwalk\Design and Performance Provisions 

1 CITY OF NORWALK 


All force mains shall have a tape attached to the pipe, identifying it as a sewer pipe. 

4. MINIMUM AND MAXIMUM SLOPE 

All sewers shall be designed and constructed to provide a mean velocity of not less than two 

(2) feet per second (fps) when flowing at the estimated average dry weather flow as 

calculated using Manning’s formula with an “n”value of 0.013. Subject to the velocity 

limitations contained in this subsection, the slope shall be the maximum possible. Drop 

manholes shall not be used to reduce slopes to the minimum allowed. 

The maximum allowable slope shall be the slope which generates a maximum flow velocity 

of 6 fps at the peak dry weather flow rate in vitrified clay pipe (VCP), and 5 fps in polyvinyl 

chloride pipe (PVC) as calculated using Manning’s equation with an “n”value of 0.013. 

The minimum slope on 6-inch sewer shall be 1% where the tributary area consists of less 

than 20 dwelling units (d.u.) or its flow equivalent. 

Sewer pipes shall have a constant slope between the upstream and downstream manhole 

of each reach. Any reach of sewer containing sags of any amount shall be removed and 

reconstructed at the design slope at no cost to the City of Norwalk. The total cost of 

inspection, administration, and retesting of improperly installed sewers shall be borne by the 

contractor. The City of Norwalk shall not accept any sewer that does not meet these 

requirements. There shall be no exception to the proper slope requirement. 

5. DESIGN FLOW CRITERIA 

The average dry weather flow (Q adw ) rates for sewers shall be calculated using the unit flow 

factors contained in Table 1 and the tributary land uses. 

Where appropriate, and when required by the City of Norwalk, the unit flow factors shall be 

evaluated by the design engineer based upon the specific land uses and densities proposed 

for new development or redevelopment. 

The peak dry weather flow (Q pdw ) in cubic feet per second (cfs) shall be determined from 

Q adw in cfs based upon the following equation: 

Q pdw =a x Q adw 

b 

Coefficients a and b shall be based upon a minimum of two weeks of flow monitoring where 

the tributary flow from a new development or redevelopment is added to an existing sewer. 

Where such information is not available, the following equation shall be used to determine 

the peak dry weather flow: 

Q pdw =1.66 x Q adw 

0.92 

The determination of the peak dry weather flow shall also consider other factors such as 

pumped flows and large sewer flow generators. 

The peak wet weather flow (Q pww ) shall be based upon recorded historical information 

where available and applicable. Otherwise, the peak wet weather flow shall be calculated 

utilizing the following formula: 




Q pww =1.35 x Q pdw 

The peak dry weather flow rate in pipes 15-inches and smaller will be limited by the 

calculated depth to pipe diameter ratio of d/D = 0.50; and 18-inches and larger d/D = 0.64. 

The pipe shall flow at a calculated depth to pipe diameter ratio of no more than 0.82 with the 

peak wet weather flow. 

Land Use 

Designation 

Table 1 

Unit Flow Factors 

Land Use 

Unit Flow 

Factor 

Units 

LDR Low Density Residential 1,870 gpd/ac 

MDR Medium Density Residential 2,080 gpd/ac 

HDR High Density Residential 3,330 gpd/ac 

NC Neighborhood Commercial 1,050 gpd/ac 

PO Professional Offices 1,050 gpd/ac 

GC General Commercial 1,050 gpd/ac 

LI Light Industrial 420 gpd/ac 

HI Heavy Industrial 840 gpd/ac 

SCH Schools 630 gpd/ac 

PARK Open Space 200 gpd/ac 

INS Institutional 1,050 gpd/ac 

6. STANDARD LOCATION AND ALIGNMENT 

In local residential and industrial streets, sewer pipes shall be located six (6) feet from the 

centerline of the street in the center of the driving lane. In major, primary, and secondary 

highways, the sewer pipes shall be located in the center of the driving lane nearest to the 

center of the street, but will not be located in the median strip or parking lanes. Any 

deviation from the standard location and alignment shall only be done with prior written 

approval of City. 

All-weather access roads capable of accommodating all required construction and 

maintenance equipment shall be provided for all sewers not located within a paved street. 

In curved streets, gravity sewer mains shall be constructed in straight reaches between 

manholes. In no case shall the outside of the sewer main be closer than four feet to the 

closest curb face. 

A maximum horizontal separation between sewer and domestic water mains shall be 

achieved by aligning the sewer on the opposite side of the street centerline from the 

domestic water main. 




7. EASEMENTS 

Permanent easements, where absolutely necessary, shall be a minimum of 30 feet in width 

and shall be shown on the plans. Temporary easements for construction only shall be 

shown on the plans including date of termination. 

Where applicable, permanent public utility easements shall be recorded on the tract map, 

and granted to the City of Norwalk. When applicable, separate easement documents for 

both permanent and temporary easements shall be prepared (on standard title company 

forms) and presented to the City of Norwalk for acceptance and recording. 

The City will accept sewers on private streets upon granting of a public utility easement to 

the City. 

The City will not accept any easement for sewers if said easement cannot be accessed with 

a flush truck through its entire length. 

Sewer easement shall be located entirely on one lot. Building set backs shall be minimum 

20 feet from easement edges. 

8. HORIZONTAL CURVES 

Gravity sewer mains shall not be designed with horizontal curves. 

9. STATIONING PROCEDURE 

Centerline stations for sewers shall be shown on the plans. Sewer centerline stations shall 

be independent of street stationing. All manholes shall be numbered and the numbers 

noted on the plans (example: MH #1). Sewer stations shall start at 1+00.00 at the 

downstream point of connection and increase upstream to the last manhole on a sewer line. 

Intersecting sewer lines will be independently stationed from their downstream point of 

connection and increase upstream to the last manhole. Each line shall be independently 

labeled for identification as “Sewer Line A”, “Sewer Line B”, etc. 

10. MINIMUM DEPTH 

Minimum depth of cover from finish street grade to the top of sewer main pipe shall be 

seven (7) feet unless otherwise approved by the City Engineer. 

Unless dictated otherwise by the elevation of an existing mainline sewer, house connections 

shall be installed so that there is a minimum of six (6) feet of cover from the top of the curb 

to the top of the pipe at the curb line. At the time of construction, stakes shall be provided 

for location and grade of each house connection. 

11. SEWER PIPE MATERIAL 

All gravity sewers shall be either extra strength VCP or SDR-26 PVC. Imperfections of any 

kind shall not be allowed in either type of pipe. Sewer service laterals shall be of the same 

material as the main line sewer-either extra strength VCP or SDR-26 PVC pipe. 




All sewer force mains carrying domestic sewage and operating at pressures of less than 40 

psi shall be PVC pipe meeting AWWA C-900 Class 200 pipe standards. All other force 

mains shall be 40 mil ceramic epoxy-lined and properly coated ductile iron pipe. 

All gravity sewers in industrially zoned areas or major commercial areas shall be extra 

strength VCP. 

12. MANHOLES 

12.1 Manhole Requirements 

A manhole will be required at: 

A. The upstream end of each line, change in grade or size, change in alignment, or 

intersection of two (2) or more sewers 

B. At a lateral when it is the same size as the main line sewer 

C. Along the sewer main at maximum distances of 300 feet for 6-inch sewers, 400 feet 

for 8-inch and larger sewers. 

12.2 Manhole Type and Size 

Manholes shall be precast reinforced concrete with eccentric cone in accordance with City 

of City of Norwalk Standard Plans S-100 through S-104. The summit manholes shall be 

precast reinforced concrete with concentric cone. Minimum diameter shall be 48 inches and 

larger sizes shall be required as shown in the following table: 

Manhole Sizes 

Maximum Branch Size Manhole Size 

(inches) 

(inches) 

8-15 10 48 30 

18-21 12 60 30 

24-36 15 72 36 

Sewer Main 

(inches) 

Extra Depth Requirements 

Depth of Cover 

(feet) 

Manhole Size 

(inches) 

6 or less 60 

6.5-12 48 

12.5-16 60 

16.5 and greater 72 

All manholes shall be provided with at least all-weather vehicular access. 

Frame and Cover 

(inches) 

Manholes constructed at a Los Angeles County Sanitation District (LACSD) facility must be 

in accordance with the LACSD standard drawings. 




12.3 Manhole Covers 

Manhole covers shall be cast iron in accordance with City of Norwalk Standard Plan S-103. 

The size shall be determined from the table in Section 12.2. Manhole covers shall have 

one (1) vent hole and one (1) pick hole. 

Temporary covers may be necessary in new streets. In these cases, the manhole shaft 

shall be left six (6) inches, minimum, below subgrade. A heavy metal plate acceptable to the 

City Engineer shall be provided to cover the manhole opening. Cleats shall be provided in at 

least four (4) points for the underside of the temporary cover to prevent the temporary cover 

from moving. These cleats shall extend a minimum of 3 inches from the cover plate and 

shall be welded to the plate. 

Plywood shall be cut to the shape and size of the manhole base and placed in the base 

before the temporary cover is placed on the shaft. At the completion of final paving, each 

manhole shall be raised to final grade by the installation of grade rings, as necessary, and 

the installation of the permanent frame and cover assembly. Plywood shall be removed 

from the manhole when the permanent frame and cover assembly is installed. 

12.4 Manhole Linings and Coatings 

The following manholes will be lined with PVC: 

A. If the sewer has a slope of 5% or greater, all the manholes on the sewer 

B. Where there is a change in slope, from steep to flat, of 3% or greater, the manhole 

at the grade change and the next manhole upstream 

C. All force main terminal manholes 

E. As required by the City Engineer 

The approved PVC liners are Ameron T-Lock liner and Koroseal Lok-Rib by B. F. Goodrich. 

Refer to Orange County Sanitation District Standard Drawing S-065 for PVC liner details. 

All other manholes shall be lined with Sancon 100 or equal. 

Outer surfaces of precast and cast-in-place manholes and structures shall be given two 

coats of bituminous dampproofing applied at a rate in accordance with manufacturer’s 

instructions. In no case shall the total bituminous coating be less than 16 mil dry film 

thickness. 

12.5 Manhole Warning Signs 

The entrance to every new manhole shall be fitted with a plastic warning sign, located 12 

inches below the top of the manhole frame, with the inscription “CAUTION – VENTILATE 

BEFORE ENTERING”in letters no smaller than ½-inch in height. The sign shall be attached 

to the concrete with four Type 316 stainless steel screws and anchors. Signs shall be 

manufactured by W.H. Brady Company; Seton Nameplate Corporation, or equal. 

R:\RPTS\Norwalk\Sewer Design Standards (April 2009) 



13. CLEAN-OUTS 

Use of clean-outs as shown in the City of Norwalk Standard Plan S-105 shall be limited to 

the following instances unless approved otherwise by the City Engineer. 

A. At the upstream end of short sections of sewer, less than 250 feet which will be 

extended within three months. 

B. All sewer laterals at the property owner’s side of the property line. 

C. Special instances such as on a sewer lateral to a single family residential lot where 

the dwelling unit is set back more than 100 feet from the property line, where there is 

a large slope up to the building pad from the property line and a grade change in the 

lateral is necessary, or where the sewer lateral enters the rear of the lot from a 

public right-of-way. 

D. On a lateral where the overflow level of the lowest wastewater fixture in the building 

is below the rim elevation of the uphill sewer manhole on the main line. In this 

situation the rim elevation of the clean-out installed at the property line shall be at 

least 6-inches below the overflow elevation of the lowest wastewater fixture on the 

lateral. A backflow prevention device is required on the lateral. 

14. SEPARATION BETWEEN SEWER AND WATER AND RECYCLED WATER LINES 

Horizontal and vertical separation between sewer mains and water and reclaimed water 

lines will be provided in accordance with the State of California Department of Heath 

Services “Criteria for Separation of Water Mains and Sanitary Sewers“. 

15. HOUSE LATERALS 

Sewer laterals shall be constructed to the property line from the main line and there shall be 

a separate lateral for each individually owned building. 

Sewer laterals shall have a minimum 4-inch diameter. Apartment and condominium 

developments shall have at least one (1) 6-inch, or one (1) 8-inch lateral to serve each 

building in the development which contains more than one dwelling unit. 

Laterals shall have a minimum slope of 2%. 

Laterals shall be located at the center of each lot and shall be constructed perpendicular or 

radial to the property line. If the developer must install a sewer lateral at a location other 

than in the center of a lot due to unavoidable interference, the improvement plans shall 

indicate the centerline station of the lateral on the sewer and show the distance from a 

property corner. In no case shall a sewer lateral be located within 12 feet of a property 

corner. Refer to Section 13 and City of Norwalk Standard Plan S-105 for cleanouts on 

laterals. 

Permanent visible monuments shall be set to indicate the locations of all sewer laterals. A 

1½-inch high “S”shall be chiseled in face of curb where the lateral crosses under the curb or 




on the edge of alleys without curbs. The method used shall be indicated on the plans. A 

licensed Civil Engineer or Land Surveyor shall verify locations of set monuments. 

The sewer laterals from the main to the building, and inside the buildings are governed by 

the Uniform Plumbing Code and enforced by the City of Norwalk Building Official. 

The sewer house laterals between the main sewer line and the property being served by the 

lateral are owned by the property owner, and NOT by the City of Norwalk. 

16. PRIVATE SEWER SYSTEMS 

All plans submitted for review and approval for commercial/industrial developments and 

residential developments with private sewer systems shall show the plans, profiles, and 

details of private onsite sewer systems. The private sewer systems shall be planned, 

designed, and constructed to the same standards as the City of Norwalk’s public sewer 

system. 

Sewer pump stations on private property shall be designed, administered, and inspected by 

the City of Norwalk or its designated representative. The private property owner shall be 

responsible for all costs associated with such design, administration, and inspection. 

Each site shall be reviewed on an individual basis at the time plans are submitted. As a 

condition of service, the City of Norwalk shall require the property owner to enter into an 

agreement with the City acknowledging that the onsite facilities are private and shall be 

properly maintained according to industry standards and the State Water Resources Control 

Board’s General Waste Discharge Requirements 2006-0003. The property owner shall 

further agree to hold the City harmless from any claims on the design, maintenance and 

operation of the private onsite systems. The property owner shall prepare an Overflow 

Emergency Response Plan and a Preventative Maintenance Plan as required by Order No. 

2006-0003 and submit it to the City for approval. 

All onsite sewer collection systems for commercial/industrial developments shall be private 

and shall be owned, operated and maintained by the property owner up to the City’s sewer 

line in a public street. A cleanout or manhole shall be installed at the owner’s side of the 

property line in accordance with City of Norwalk Standard Plans S-105 or S-100 through S- 

104. Each building onsite shall have an individual sewer lateral with a monitoring manhole. 

Monitoring manholes shall be installed in accordance with City criteria. All laterals from a 

building shall be connected to the main lateral upstream of the monitoring manhole for that 

building. No lateral connections are to be made downstream of the monitoring manhole. 

17. SEWER PUMP STATIONS 

17.1 General 

All sewer pump stations conveying wastewater flows to the City of Norwalk’s collection 

system, including those from private systems, shall be designed, administered, and 

inspected by the City of Norwalk, or its authorized representative. 

The general criteria outlined herein shall apply to all sewer pump stations. The detailed 

design criteria for each sewer pump station will be established based upon the specific 




conditions of each installation on a case-by-case basis and documented in a preliminary 

design report. Sewer pump stations shall be designed according to the following criteria: 

Small sewer pump stations, where the peak wet weather flow can be pumped with a 

maximum of two duty pumps of 1,500 gpm capacity, shall be the stainless steel slide-rail 

submersible type with a minimum of two recessed impeller or enclosed screw impeller 

centrifugal pumps, permanent standby generator/automatic transfer switch, and peak flow 

storage. 

Larger sewer pump stations shall be wet well-dry well type with permanent standby 

generator/automatic transfer switch, and peak flow storage. The City Engineer may allow 

slide rail submersible pump stations if project conditions warrant it. Pumps shall be either 

the recessed impeller, or enclosed screw impeller type, as determined by the City Engineer. 

17.2 Standards and Codes 

Sewer pump station designs shall be based upon current codes and standards, including 

but not limited to: 

• Statewide General Waste Discharge Requirements covered under Order No. 2006- 

0003 issued by the State Water Resources Control Board on May 2, 2006 

• Hydraulic Institute Standards 

• California Administrative Code, Title 8, Article 59-Electrical Safety Orders 

• National Electrical Code 

• NFPA 820 Fire Protection in Wastewater Treatment Plant and Collection System 

Facilities 

• Uniform Building Code 

• Uniform Plumbing Code 

• Uniform Mechanical Code 

• California Fire Code 

• National Electrical Manufacturers Association (NEMA) 

• American Society of Heating, Refrigerating, and Air Conditioning Engineers 

(ASHRAE) 

• Standard Specifications for Public Works Construction 

• Standard Plans for Public Works Construction 

• OSHA Construction Safety Orders 

• American Water Works Association 

• American Society for Testing Materials 

17.3 Design Flows and Heads 

The pump stations shall be designed with a firm pumping capacity equaling the greater of: 

• Tributary peak wet weather flow 




• Flow that will provide a minimum velocity of 3 fps in the force main. 

The standby pump will have the same capacity as the largest pump in the pump station. 

In selecting the number, capacity, and operating characteristics of the pumps, the minimum, 

average, peak dry weather and peak wet weather flows, as well as wet well size and 

operating band shall be considered. The selected design shall minimize pump cycling and 

odors. 

The total dynamic head (the sum of static lift, velocity head, and frictional losses in the 

station piping/ valving and force main) shall be determined for all operating conditions, wet 

well and discharge point water surface elevations, and a range of frictional coefficients 

(Hazen Williams C factor of 80 to 150). 

Calculations documenting the determination of flows and head calculations shall be 

submitted along with pump curves and catalog information for the recommended pumps. 

Prior to final acceptance, the design engineer shall obtain written verification from the 

recommended pump manufacturers that the selected pumps shall perform throughout their 

operating range as designed at the published efficiencies free from cavitation, vibration, and 

premature failure. 

17.4 Drivers 

The pumps shall be driven by submersible or vertical dry pit immersible motors. All motors 

shall be Factory Mutual (FM) or Underwriters Laboratories, Inc. (UL) listed explosion proof 

type. Variable frequency drives shall not be allowed if the velocity in the force main drops to 

below 3 feet per second at any operating condition. Motors operated by variable frequency 

drives shall be inverter duty motors. Nameplate horsepower shall be at least 20 percent 

greater than the maximum brake horsepower needed within the operating range of the 

pump. 

Variable frequency drives shall be provided with bypass contactors to operate the pumps at 

full speed. 

Small pump stations may be designed with constant speed pumps. Larger pump stations 

may require the use of variable speed drives. The decision of the City Engineer of the City 

of Norwalk shall be final as to the type of driver to be used. 

17.5 Wet Well 

The wet well shall be sized to 

• Provide adequate submergence 

• Provide adequate net positive suction head available (NPSHA) 

• Prevent frequent pump cycling 

• Provide emergency storage 




Submergence provided shall prevent formation of vortices and air being drawn into the 

pump. It shall also prevent cavitation. The minimum submergence shall be at least one foot 

greater than that required by the pump manufacturer. 

The net positive suction head available shall be calculated as: 

Where 

NPSHA=2.24 (P a -P v )-H l +Z 

P a = 

P v = 

H l = 

Atmospheric pressure (psia) 

Vapor Pressure of liquid at the maximum expected temperature (use 0.59 psia) 

Friction and minor losses between the wet well and the pump suction flange in feet of 

liquid 

Z= Difference in elevation between the minimum wet well water level and pump datum, in 

feet. Use –when the pump datum is higher than the minimum wet well water level. 

The minimum NPSHA shall be at least eight feet greater than the net positive suction head 

required (NPSHR) by the selected pump for the maximum expected flow through the pump. 

The wet well shall be sized to provide the storage capacity which will preclude exceeding 

the following number of pump starts per hour: 

Motor 

Horsepower 

Maximum Starts 

per Hour 

Minimum Cycling Time 

(Minutes) 

Up to 20 6 10 

25 to 50 4 15 

60 to 75 3 20 

100 and larger 2 30 

Wet well bottom corners shall be sloped at 1:1 and slope to the suction pipe inlet to prevent 

the accumulation of debris on the wet well floor. 

Influent pipe(s) shall not enter the wet well in a position which may cause pre-rotation of the 

flow into the pump suction, and turbulence in the wet well. The influent velocity into the wet 

well shall be no greater than three (3) feet per second. 

For large pump stations, a partition wall(s) with sluice gates may be required to isolate a 

portion of the wet well for cleaning. 

17.6 Emergency Storage 

Emergency storage volume needed shall be evaluated for each pump station based upon 

the tributary area and expected ultimate wastewater flows. The minimum volume of 

emergency storage shall be 30 minutes of ultimate peak wet weather flow without 

surcharging the tributary collection system. The emergency storage volume may be 

provided in the wet well or in separate adjacent PVC lined overflow structure. 




Where possible, the invert of the overflow structure shall be higher than the low water 

elevation of the pump station wet well to allow gravity drainage of the stored sewage to the 

wet well. There shall be a minimum of two connecting pipes between the overflow structure 

and the wet well. The connecting pipes shall be equipped with flap gates or Tide-Flex check 

valves on the wet well side. The floor of the overflow structure shall slope to the connecting 

pipes. 

All overflow structures shall be equipped with an access hatch, and three 30-inch diameter 

maintenance access holes. A 2-1/2 inch hydrant water connection shall be provided near 

the overflow structure for use in periodic cleaning. The water supply to the hydrant water 

connection shall have a reduced pressure backflow preventer. 

The higher of the maximum storage level and overflow level shall be set at least one foot (1- 

ft) lower than the top of the lowest manhole in the system, basement or p-trap of the 

plumbing fixture connected to the system. 

17.7 Dry Well 

The dry well shall meet the following criteria: 

A. Pumps shall be placed to provide minimum clear space of 3’-6” 

B. The lowest level of the pump station dry well shall have a sump pit with duplex 

explosion proof submersible pumps controlled by float switches. The sump pumps 

shall discharge to the wet well above the maximum water level. 

C. Discharge piping and the force main shall be placed in the dry well along the 

common wall with the wet well. The flow meter shall be placed inside the dry well 

sufficiently downstream of the last pump discharge pipe. If there is not sufficient 

room, the flow meter shall be placed in a below grade vault adjacent to the pump 

station structure. 

D. Catwalks or mezzanine levels shall be provided to access the flow meters, valves, 

and other portions of the equipment 

17.8 Standby Equipment 

All pump stations shall have standby equipment capable of handling the ultimate peak wet 

weather flow during a commercial power outage and/or with the largest unit out of service. 

This criterion shall apply to all essential electrical and mechanical equipment including 

pumps/motors, fans, air compressors and sump pumps. 

There shall be a minimum of one standby main sewage pump equal in size to the largest 

duty main sewage pump in the station. 

All pump stations shall have a permanent standby generator and an automatic transfer 

switch sized to start and operate all the sewage pumps needed for ultimate peak wet 

weather flow, sump pump, ventilation fans, lighting, instrumentation, controls, and telemetry, 

with voltage dip not to exceed 16% when starting any motor. 




Generators shall be skid mounted, permanently anchored to the foundation, and housed in 

an acoustically insulated enclosure. Exhaust mufflers shall be super critical grade designed 

for noise level not to exceed the noise level allowed within each particular area. 

Load banks sized for 80% of the generator capacity shall be provided. Load banks shall be 

mounted in the vicinity of the generator and protected with adequate enclosure suitable for 

the location as required by NEMA Standards. 

Portable trailer mounted generators are acceptable only for locations where installation of a 

permanent skid-mounted generator is not feasible. When a portable trailer mounted 

generator is furnished, a power receptacle shall be permanently installed for quick 

connection. 

Standby generators shall be furnished with battery chargers and block heaters. 

The standby generator shall be a diesel or natural gas powered generator. The diesel fuel 

powered generators shall be equipped with a sub-base fuel tank sized for a minimum of 12 

hours of continuous full load operation. Standby generators shall be units pre-approved by 

the South Coast Air Quality Management District. 

17.9 Pumps 

Pumps shall be the enclosed screw-centrifugal or recessed impeller type. Wet well-dry well 

pumps shall be suitable for operation when the dry well is flooded. Pumping capacity and 

head shall be considered in the selection of the type of pump for the wet well-dry well pump 

stations. 

RECESSED IMPELLER CENTRIFUGAL PUMPS 

Recessed impeller centrifugal pumps are designed to handle stringy materials and up to 25 

times the amount of solids of conventional non-clog pumps. Some recessed impellers are 

labeled by pump manufacturers as torque-flow, bladeless and sphere flow. However, all of 

these pump models follow the general design of placing the impeller away from the fluid 

stream in order to pass stringy material without clogging the hydraulic passages. 

The recommended minimum design criteria in the selection of recessed impeller centrifugal 

pumps are as follows: 

a. Pump impeller shall be selected with the best possible efficiency at design point or at the operating 

range of the pump. 

b. Maximum Speed 1750 rpm or shall not exceed the limitation as recommended by the Hydraulic 

Institute Standards for Centrifugal Pump application 

c. Materials of 

Construction 

• NiHard (minimum of 550 Brinnell hardness) or stainless steel Type 316 

impeller with a removable wear plate of the same material as the impeller 

• NiHard (minimum of 550 Brinnell hardness) or cast iron casing, as 

determined by the City Engineer. 

• Stainless steel Type 316 shaft. 

• Tandem mechanical shaft seal system for the motor with two totally 

independent seal assemblies and Tungsten-Carbide seal faces 




d. Upper and Lower 

Bearings 

e. Slide Away 

Coupling 

Radial and thrust bearings, grease lubricated with minimum B-10 bearing life 

of 60,000 hours for the operating range of the pump. 

Foot mounted discharge elbow and adaptor, base plate, upper and lower rail 

supports, lifting yoke, and cable. All metal to metal interfaces where 

movement may occur shall be non-sparking. 

f. Electric Motor • For wet well installation, motors shall be FM or UL listed, and be 

designed for Class I, Group D, Division 1 explosion proof. 

• NEMA Design B, heavy duty, high efficiency, non-overloading, with a 

nameplate horsepower at least 20% greater than the maximum 

horsepower required over the entire operating range. 

• Thermal overload protectors imbedded in the motor windings. 

• Dual moisture or leak sensors on the sealing chamber. 

• Motors shall be immersible capable of operating continuously in air 

without the use of sewage pumped for cooling if installed in a dry well. 

• Motors in damp locations and dry pits shall have two cycles of solid 

baked epoxy vacuum impregnation. 

• Motors shall be inverter duty if operated by variable frequency drives. 

g. Painting and Coating All non-stainless steel wetted surfaces in contact with wastewater shall be 

coated with coal tar epoxy enamel. Surface preparation shall be in 

accordance with SSPC-SP5, white metal blast cleaning. Prime coat to 

DFT=l.5 mils, Amercoat 71, Engard 422 or equal. Two or more coats, 

DFT=16 mils, Amercoat 78HB, Engard 464 or equal. Total system DFT=17.5 

mils. 

All non-stainless steel external surfaces exposed to corrosive environment 

shall be coated and painted by amine-cured epoxy. Surface preparation 

shall be in accordance with alkaline cleaned, SSPC-SP1. Prime coat and 

finish coat shall be three or more, DFT=16 mils. Amercoat 395, Engard 480 

or equal. 

SCREW-CENTRIFUGAL PUMPS 

The recommended minimum design criteria in the selection of the screw-centrifugal pumps 

are as follows: 

a. Pump impeller shall be selected with the best possible efficiency at design point or at the operating 

range of the pump. 

b. Maximum Speed • 1750 rpm for pumps with discharge nozzle diameter up to 12-inch, 

• 1175 rpm for pumps with discharge nozzle diameter from 14 to 16-inch, 

• Shall not exceed the speed limitation recommended by the Hydraulic 

Institute Standards for Centrifugal Pumps. 

• 




c. Materials of 

Construction 

• Cast iron with Hi Chrome suction liner or 316 Stainless steel where 

available 

• Stainless steel Type 316 impeller and shaft. 

• Tandem mechanical shaft seal system for the motor with two totally 

independent seal assemblies and Tungsten-Carbide seal faces and 

silicone carbide lower seal 

• Minimum B-10 bearing life of 60,000 hours for the operating range of the 

pump. 

d. Electric Motor • For wet well installation, motors shall be FM or UL listed, and be 

designed for Class I, Group D, Division 1 explosion proof. 

• Thermal overload protectors imbedded in the motor windings. 

• Dual moisture or leak sensors on the sealing chamber. 

• Motors shall be NEMA Design B, heavy-duty, high efficiency with Class B 

or F insulation. Motors shall be non-overloading over the entire 

operating range, with a nameplate horsepower rating a minimum of 20 

percent greater than the maximum horsepower required over the 

operating range. 

• Motors located in a damp environment and in a dry pit shall have 2 cycles 

of solid baked epoxy vacuum impregnation. 

• Motors shall be inverter duty if operated by variable frequency drives. 

• Motors shall be immersible, capable of operating continuously in air 

without the use of sewage pumped for cooling if installed in a dry well. 

e. Painting and Coating All non-stainless steel wetted surfaces in contact with wastewater shall be 

coated with coal tar epoxy enamel. Surface preparation shall be in accordance 

with SSPC-SP5, white metal blast cleaning. Prime coat to DFT=1.5 mils, 

Amercoat 71, Engard 422 or equal. Two or more coats, DFT=16 rails, 

Amercoat 78HB, Engard 464 or equal. Total system DFT=17.5 mils. 

17.10 Valves and Gates 

Non-stainless steel external surface exposed to corrosive environment shall 

be coated and painted by amine cured epoxy. Surface preparation shall be in 

accordance with alkaline cleaned, SSPC-SP1. Prime coat and finish coat shall 

be three or more, DFT=16 mils. Amercoat 395, Engard 480 or equal. 

Pump stations are equipped with various types of valves to prevent backflow, to isolate the 

equipment from the system, to control hydraulic surges and to drain the piping system 

during scheduled repair and maintenance. Each valve type differs in construction, 

materials, and operation depending on the service and application. All valves shall be 

suitable for wastewater service. 

All interior surfaces of valves in contact with wastewater shall be epoxy coated. All valves 

10-inch diameter and larger shall be provided with motor operators. Manually operated 

valves located more than six feet above the operating floor shall be equipped with chain 

wheel operators, with the chain extended 36 inches above finish floor. Motor operated 




valves shall be provided with a manual hand wheel and manual push button station 

conveniently located below the valve, 5 feet above finished floor. 

SLUICE GATES 

Sluice gates shall be furnished with stainless steel frames and slides with embedded bronze 

seats, Type 316 stainless steel stem, and adjustable bronze bushed stem guides. Sluice 

gate manual operator shall have AWWA square nut; manual crank operator with floor stand 

and 2-speed gear reducer designed for opening time of not to exceed six minutes. Motor 

operator shall be provided when required by the City Engineer. Motor operated gates shall 

be designed for opening and closing times of one foot per minute. 

Sluice gates shall be specified to be furnished with pattern wall thimbles to match the 

concrete thickness where the gate is to be installed. 

Sluice gates shall be Rodney Hunt or approved equal. 

ECCENTRIC PLUG VALVES 

Non-lubricated eccentric plug valves shall be used as isolation valves. Valves shall have 

hard rubber (suitable for sewage service) resilient faced plugs and flanged ends. Valve 

seats and discs shall be stainless steel, Type 316. Bodies shall be semi-steel with raised 

seats. Valves shall be of the bolted bonnet design. Valve design shall allow repacking 

without removing the bonnet, and the packing shall be adjustable. All exposed nuts, bolts, 

springs, and washers shall be stainless steel, Type 316. Valves shall have permanently 

lubricated stainless steel bearings in the upper and lower plugstem journals. 

Manual valves shall have a 2-inch square nut and lever actuator. Levers shall be field cut 

as required to be operable in their installed locations. 

Eccentric plug valves may be used as pump control valve to alleviate hydraulic surges 

during normal starting and stopping of the pumps and as surge anticipators when required. 

These valves shall have hydraulic cylinder type operators with adjustable opening and 

closing times. Where the valve is used as a surge relief valve, emergency (upon failure of 

power supply) opening and closing times shall be specified. 

Where space permits, all eccentric plug valves shall be installed with the shaft in the 

horizontal position. The orientation of the plug with respect to the fluid flow direction shall be 

as recommended by the manufacturer. The valve manufacturer’s recommended installation 

instructions to prevent clogging of the valves during extended shutdown periods shall be 

strictly followed. 

Valves shall have unobstructed port area of not less than 80-percent of total pipe area. 

Eccentric plug valves shall be as manufactured by DeZurik Corporation, Keystone, Drum- 

Owens (Homestead), Milliken, or approved equal. 




BALL VALVES 

When required by the City Engineer, ball valves shall be used as pump control valves or for 

surge relief where flow characteristics require the valve trim that would match that of the ball 

valves. 

Small diameter ball valves (3/4 inch to 2-1/2 inch diameter) shall be used as isolation shut 

off valves for potable or pump station water system. 

All ball valves shall be in accordance with ANSI/AWWA C 507, with cast iron, ductile iron, 

cast steel, or stainless steel bodies, support legs or pads, flange ends, suitable for velocities 

up to 35 fps, temperatures up to 125 degrees F, and design pressures to 150, or 250 psi 

depending on the pressure range required by the system. The balls shall be cast iron, 

ductile iron, cast steel or stainless steel, shaft or trunion-mounted, with tight shut-off, single 

or double seat, and full bore. The valves shall be rubber, with stainless steel or monel 

shafts, and at least one thrust bearing. Except for stainless steel, ferrous surfaces of valves 

in contact with wastewater shall be minimum 16 mil epoxy-coated. 

Ball valves shall be as manufactured by Jamesbury Corporation, Wm. Powell Company, or 

approved equal. 

CHECK VALVES 

Check valves shall be installed at each pump discharge piping to prevent backflow of 

wastewater which can cause severe damage to the pump impeller and shaft, and 

recirculation of flows back to the wet well in stations with multiple pumps. Valves shall 

comply with the requirements of AWWA C508. 

Check valves shall be the outside lever and weight type swing check valves. They shall be 

installed in the horizontal position to prevent accumulation of solids downstream of the valve 

which can cause clogging of the valves. 

Swing check valves shall have a flanged cover piece to provide access to the disc. The 

valve body, cover, and disk shall be cast iron conforming to ASTM A 126 Grade B. Disc 

facing shall be rubber conforming to ASTM D2000 2BG715. Seat ring and clapper arm shall 

be cast bronze conforming to ASTM B584 Alloy C 84400. Clapper arm shall be clamped to 

the hinge pin with stainless steel screws and jam nuts. 

Ferrous surfaces of valves in contact with wastewater shall be minimum 16 mil epoxy 

coated. 

Swing check valves shall be as manufactured by APCO (Valve and Primer Corp.), Kennedy, 

Crane Company, or approved equal. 

SEWAGE SURGE RELIEF VALVES 

The necessity for surge control devices shall be determined through a complete surge 

analysis of the pumping system. Although surge tanks are the most reliable means to 

alleviate damaging surges in the force mains, sewage surge relief valves may be required 

by the system. Where surge relief valves are required, the valve shall be installed in the 

discharge piping manifold and connected to the wet well. The valve shall be designed to 




open immediately when the system pressure exceeds the load setting of the counterweights 

and shall close slowly at an adjustable speed upon return of system pressure to normal. 

The surge relief valve body shall be constructed of a heavy cast-iron or cast steel disc 

having rubber seating face; and corrosion resistant shaft and cushion chamber. 

Sewage surge relief valves shall be as manufactured by APCO (Valve and Primer 

Corporation), Empire Specialty Co., Inc, or approved equal. 

SEWAGE AIR RELEASE VALVES 

Sewage air release valves shall not be used unless absolutely necessary. The design 

engineer shall endeavor to provide a system which rises continuously from the pump station 

to the discharge point. Where absolutely necessary, sewage air release valves shall be 

provided to vent accumulating air or gas during pumping operation or entrapped during 

initial operation. Air release valves shall be installed at high points of the piping systems. 

Entrapped air or gases can reduce pumping capacity of the pumping system or cause 

corrosion of the piping system with gases containing hydrogen sulfide. The air or gas vent 

located at the pump station plant shall be discharged to the wet well. 

The valves shall have long float stems and bodies to minimize clogging. Each valve shall be 

furnished with backwashing accessories to remove solids accumulated inside the valve. 

Water supply and connection shall be provided with appropriate reduced pressure backflow 

preventer near the valve for backwashing. 

Sewage air release valves shall be as manufactured by APCO (Valve and Primer 

Corporation), Val-Matic (Valve Manufacturing Corporation), or approved equal. 

REDUCED PRESSURE BACKFLOW PREVENTERS 

Backflow preventers shall be installed where utility water or plant water is connected to the 

potable water supply to prevent contamination of the potable water system. The valves shall 

be designed to operate on the reduced pressure principle. The valve assembly shall consist 

of two spring loaded check valves, automatic differential pressure relief valve, drain valves 

and shut-off valves. The body materials shall be bronze for working pressure of not less 

than 150 psi, with bronze and stainless steel trim. Drain lines and air gaps shall be 

provided. All backflow preventers shall be registered with County Health Department and 

must be approved for use in the City of Norwalk. 

Backflow prevention valves shall be as manufactured by Cla-Val Company or Febco. 

PUMP CONTROL VALVES 

The pump control valves shall be installed in the pump discharge pipe to minimize hydraulic 

surges during normal starting, stopping and emergency stopping of the pump during power 

failure or emergency stopping caused by system failures. 

The pump control valve shall be operated by hydraulic (oil) or pneumatic operator with a 

reserve accumulator system as back-up energy source to operate the valve during power 

failure. The pump control system shall be designed to start the pump against a closed valve. 

Once the pump has developed pressure, the pump control valve shall start to open until it 




eaches the maximum open position. Stopping sequence shall cause the pump control 

valve to close. Complete closure of the valve shall signal the pump to stop. Emergency 

power failure shall cause the pump control valve to close. 

The normal opening, closing, and emergency closing times of the pump control valve shall 

be independently adjustable. Range of adjustment shall be determined based upon the 

results of surge analysis. Final settings of closing and opening times shall be verified during 

pump station start-up. Settings shall be included in the Operation and Maintenance Manual. 

17.11 Magnetic Flow Meters 

Each pump station shall be equipped with metering equipment to measure outlet flow and 

provide flow signal for recording, totalizing and control of other equipment. In addition, the 

flow meter shall be used for pump field performance test to measure capacity and efficiency. 

The meter shall be magnetic type suitable for wastewater service. 

Magnetic flow meters shall be provided at the pump station discharge manifold capable of 

metering the full range of flow with an accuracy of ±1 percent of flow rate from 10 to 100 

percent of scale. At a velocity below 1 foot per second, the accuracy shall be ±0.1 percent 

of the full scale. The meter shall be installed in the piping manifold with minimum straight 

approach of 4 and 2 diameters upstream and downstream respectively. 

The size of the flow meter shall be selected to cover the entire velocity range expected. 

The magnetic flow meter shall utilize characterized electromagnetic induction to produce a 

voltage linearly proportional to the average flow rate. The metering system shall consist of a 

sensor with field coils, transmitter and interconnecting cables to make a complete operating 

flow metering system. The meter shall be bipolar pulsed dc type with continuous automatic 

zeroing. 

The sensor shall be flange tube with non-conductive liner. The tube shall be constructed of 

Type 316 stainless steel with carbon steel flanges AWWA Class D if the coils are external to 

the tube. The sensor rating shall be NEMA 4, and capable of withstanding accidental 

submergence in water to a depth of 30 feet for 48 hours. The meter shall include a positive 

zero feature for periods when the metering portion of the process pipe is not full. 

Liner material shall be neoprene, except for liquids which may deposit non-conductive 

coatings, which shall have Teflon linings. The specific conductivity of the liquid shall not 

preclude meter operation. 

Grounding electrodes shall be of the same material as the sensing electrodes and shall be 

furnished mounted on each end of all flanges. 

Transmitters shall be provided for either local or remote indication as required for each 

particular project. Remote transmitters shall be NEMA-4X enclosures suitable for wall 

mounting. Transmitters shall produce a 4-20 ma-dc output signal into a minimum load of 800 

ohms linear flow, and a scaled pulse for totalization. All electrical equipment furnished with 

the magnetic flow meter shall carry a UL label. 

Magnetic flow meters shall be Tigermag manufactured by Sparling Instrument Co., Inc. or 

approved equal. 




The accuracy of the installed meters shall be verified by wet well level, volume, and time 

measurements prior to startup testing Meters not meeting the accuracy requirements shall 

be replaced at no cost to the City. 

17.12 Piping and Support System 

The pump station piping and supports system consists of the gravity sewer, pump suction 

and discharge piping, station water or utility water piping, potable water piping, air piping, 

sanitary drainage piping, fire protection, and sprinkler piping systems. Most of these piping 

systems are adequately specified by the applicable sections of the Uniform Plumbing Code, 

Fire Codes and the Standard Specifications for Public Works Construction. 

This Section includes special requirements and recommended practices involving the 

design of piping and the support system. 

A. Piping 

1. Materials 

Ductile iron pipe shall be used in pump station main piping, consisting of 

suction and discharge piping, discharge manifolds, force mains as specified 

in Section 11, and water piping 2-1/2 inch and larger. Ductile iron pipe shall 

be in accordance with SSPWC, and ANSI A21.5l (AWWA C151). All internal 

surfaces of ductile iron pipe and fittings for water service shall be cement 

mortar lined and sealed with bituminous coating in conformance with AWWA 

C104. Internal surfaces of ductile iron pipe for sewer service shall be lined 

with polyurethane or glass. 

Unless otherwise specified, all joints of ductile iron pipe shall be 125-lb flange 

in conformance with ANSI B16.1, B16.2 and A21.10 (AWWA C110). Sleeve 

or mechanical grooved type couplings shall be provided at the suction and 

discharge piping of the pump, and between the magnetic flow meter and the 

isolation valves to allow removal of the equipment for maintenance. 

All bolts shall be of Type 316 stainless steel with bronze nuts or cap screws 

of copper— copper silicon alloy, conforming to ASTM B 98, Alloy C 65100, 

designation H04, or alloy C 65500, designation H04. Where anaerobic 

conditions are anticipated, Type 304 stainless steel shall be used. 

Mechanical-type couplings (grooved) shall be used between the valves, 

pumps, meters and the piping system for the above ground installation. 

Groove type couplings shall not be used for underground installation. 

Mechanical-type couplings shall be cast as manufactured by Victaulic, Gustin 

Bacon or equal. 

Sleeve-type couplings shall be of fabricated steel with steel bolts and with 

sizes to fit outside diameter of the ductile iron pipe. The middle ring shall not 

be less than 1/4-inch in thickness and minimum of 5 to 7-inches long. The 

follower shall be single piece contoured mill section welded and coldexpanded 

as required for the middle rings. The coupling shall be equipped 




with a gasket to make the joint water-tight. The coupling shall be factory 

epoxy coated suitable for sewer service. 

Sleeve couplings shall be installed in the piping systems subject to differential 

settlement as in the force main that connects the piping inside the pump 

station building to the yard piping. Two sets of sleeve couplings shall be 

installed with spacing as recommended by the coupling manufacturer. 

Where sleeve couplings are installed in the piping system subject to thrust 

loads, the coupling shall be provided with restraining bolts. The bolts shall be 

designed in conformance with AWWA Design Manual M-11. 

Sleeve-type couplings shall be as manufactured by Rockwell (Smith-Blair), or 

Dresser. 

2. Suction Pipe 

The suction pipe shall meet the following requirements: 

a. The suction pipe shall be sized to provide a minimum velocity of 3 feet 

per second, and a maximum velocity of 6 feet per second throughout 

the operational range of the pump. 

b. The inlet velocity to the eye of the impeller shall meet the pump 

manufacturer’s requirements. The largest suction inlet available shall 

be selected. 

c. The suction pipe shall be flat, or slope up to the pump to eliminate the 

formation of air pockets. Reducers shall be the eccentric type, with 

flat top, matching the crown of the suction pipe. 

d. There shall be a straight length of pipe of minimum 5 diameters before 

the suction elbow to provide uniform flow to the pump. 

e. The inlet of the suction pipe shall be a long radius elbow with a flared 

bell. The inlet location shall be in accordance with the hydraulic 

institute standards. The velocity at the inlet to the suction bell shall be 

less than 2.5 feet per second. 

f. The suction line isolation valve shall be full port eccentric plug valve 

located close to the wet well wall, allowing sufficient room for removal 

of the bolts and servicing of the valve. 

g. A pressure gauge capable of measuring the entire range of pressures 

expected at the entrance to the pump shall be provided as close to 

the pump as possible. The gauge shall be installed on a ½ inch NPT 

pipe tap with a ball isolation valve and chem seal with snubber. 




3. Discharge Pipe 

The discharge pipe shall meet the following requirements: 

a. Discharge pipes shall be sized for a minimum velocity of 3 feet per 

second and a maximum velocity of 6 feet per second. 

b. The discharge nozzle for dry well installed pumps shall be directed 

towards the wet well and rotated 45 degrees from the suction line. 

c. The discharge pipe shall be connected to the discharge header at an 

angle of 45 degrees. 

d. A pressure gauge shall be installed on the discharge nozzle or as 

close to the pump as possible. The gauge shall be installed on a ½ 

inch NPT diameter pipe tap with a ball isolation valve and chem seal 

with snubber. 

e. A 1-1/2 inch diameter pipe with a ball isolation valve shall be installed 

between the top of the pump casing and the wet well. 

B. Pipe Support Systems 

All piping systems, including connections to equipment, shall be designed with 

proper support to prevent undue deflection, vibration, and stresses on piping, 

equipment, and structures resulting from normal operation and seismic events. All 

supports and parts thereof shall conform to the requirements of ANSI/ASME B 31.1 

except as specified herein. 

Ductile iron pipe of any size shall have a minimum of 2 supports per straight length 

not to exceed 10 feet of unsupported span. One of the supports shall be located at 

the joint. 

Where the piping system is subject to thrust as a result of hydraulic surge or 

actuation of a surge relief valve, a thrust support or a hydraulic shock suppressor 

shall be provided. 

All pipe supports shall be galvanized after fabrication. Pipe supports shall have a 

minimum of 1-1/2 inch thick dry pack between the floor and the support base. 

17.13 Ancillary Equipment 

Each pump station shall be designed to provide the necessary ancillary equipment to 

support the operation and maintenance of the facility. This equipment is essential to the 

operation and maintenance of the system. Ancillary equipment or systems that are 

discussed herein are commonly required equipment or systems in a wet well-dry well pump 

station. 




A. Hoisting Equipment 

Most pump stations are located underground to provide adequate submergence for 

the pumps. Therefore, the substructure and superstructure need to be designed to 

allow for installation and removal of equipment. The provisions for access hatches, 

lifting hooks, hoisting systems, roll-up doors and other means to provide ease of 

maintenance shall be carefully investigated and designed as required. 

For wet well-dry well type pump stations equipped with either vertical non-clog dry 

well pumps or submersible pumps mounted in the dry well, a traveling bridge crane 

shall be provided. The bridge crane shall be designed to have a travel and span 

capable of reaching the pumps, meters and valves. Where the valves are located in 

areas which are inaccessible to the crane, lifting eyes attached to the ceiling shall be 

provided directly above the valve or equipment. A floor access hatch shall be 

provided when required. 

Bridge cranes shall have a manually or electrically operated hoist, trolley and end 

trucks, all designed to conform to all applicable codes, and OSHA safety 

requirements. Where possible, monorail hoists may be used in lieu of the traveling 

bridge cranes. 

Where space permits, a hoisting system shall be designed to allow direct transfer of 

equipment from the dry well to a flat bed truck. Traffic into the pump station building 

shall be given special consideration and necessary turning radius shall be provided. 

B. HVAC and Odor Control Systems 

A typical pump station consists of the wet well, dry well or the pump room, motor 

room, electrical and control room, and ancillary equipment rooms. Each of these 

rooms requires different methods and degrees of heating, air conditioning and 

ventilation to provide the following conditions: 

1. A safe and comfortable working environment for personnel; 

2. To facilitate proper operation of equipment; 

3. To minimize corrosion of equipment and building materials; and 

4. To prevent accumulation of explosive and hazardous gases. 

The heating, ventilating and air conditioning (HVAC) system and odor control 

systems shall be designed and controlled as one integrated system. Air distribution, 

building enclosures, wall penetrations, wind directions, building occupancies, and 

area classifications shall be carefully investigated. HVAC systems shall be designed 

in accordance with the American Society of Heating, Refrigerating and Air 

Conditioning Engineers (ASHRAE), State of California Energy Conservation 

Standards Title 24 and the NFPA 820 Fire Protection in Wastewater Treatment 

Plants. 

Equipment conveying corrosives shall be of material that is corrosion resistant, such 

as fiberglass reinforced plastic (FRP) or stainless steel. If FRP ductwork is used, it 




shall have flame spread of less than 25, and a smoke propagation of less than 400, 

and be of fire resistant rating. Air containing flammable and explosive vapors or toxic 

gases shall not be recirculated. 

Air conditioning may be required for pump stations with VFD’s. 

Depending upon classification, motors for supply and exhaust fans shall be explosion 

proof, totally enclosed fan cooled (TEFC) units. 

C. Wet Well Ventilation 

The pump station wet well receives and stores wastewater before it is pumped to the 

force main. Corrosive and hazardous gases are normally present in the wet well. 

These gases can become a safety hazard to operating personnel or can cause 

corrosion of building materials and equipment in the wet well. In order to minimize 

accumulation of gases inside the wet well, the wet well shall be flushed with fresh air 

by an adequately sized ventilation system. 

Ventilation rates shall be in accordance with: 

1. NFPA 820 Fire Protection in Wastewater Treatment Plants 

2. Occupational Health and Safety Act (OSHA) 

Pump station wet wells are classified into two types depending on their use; 

1. Accessible Wet Well. 

2. Sealed Wet Well. 

ACCESSIBLE WET WELLS 

Wet wells which require routine access for maintenance shall be provided with 

adequate fresh air ventilation in order to provide a safe environment for maintenance 

personnel, to prevent accumulation of explosive gases, and to minimize corrosion of 

equipment installed in the wet well. The internal surfaces of the wet well shall be 

lined with PVC for corrosion protection. 

The following minimum ventilation criteria shall be used: 

1. All accessible wet wells shall be provided with continuous ventilation of a 

minimum of 15 air changes per hour. 

2. Where intermittent ventilation is required, the ventilation rate shall be at least 

30 air changes per hour. 

All electrical equipment and fans inside the accessible wet well shall be explosionproof 

designed and manufactured for Class I, Division I, Group D. All other design 

criteria shall be in accordance with NFPA 820 Fire Protection in Wastewater 

Treatment Plants. 




SEALED WET WELLS 

Sealed wet wells shall be designed to be low maintenance. The internal surfaces of 

the wet well shall be lined with PVC for corrosion protection. 

Sealed wet wells shall be provided with static vents to accommodate air 

displacement due to the rise and fall of the water level in the wet well. The vent shall 

have a minimum diameter of one-half the diameter of the incoming sewer. The vent 

pipe shall be connected to the nearest sewer maintenance hole where possible. 

Where the pump station is located away from any sensitive area, vent pipe could be 

extended above the roof line with a minimum of 15 feet from any window or fresh air 

inlet. 

All electrical equipment inside the sealed wet well shall be classified in accordance 

with NFPA 820, Fire Protection in Wastewater Treatment and Collection System 

Facilities. 

C. Odor Control 

The need for odor control systems shall be evaluated for each project. Such 

evaluation shall be based on a life cycle cost of 20 years with major consideration of 

the power and chemical consumption, first cost, maintenance cost, reliability and 

efficiency of the system. 

Wet well odor control shall consist of a water misting system. Activated carbon 

scrubbers, chemical scrubbers utilizing a chemical absorption process for removal of 

odors, or chemical or air injection systems may be necessary for odor control in other 

parts of a pump station. 

For the chemical scrubbing systems, foul air from the plant process facility is 

introduced into the scrubber vessel with an atomized mist chemical solution 

containing sodium hypochlorite. Oxidation of odorous compounds occurs upon 

contact with the scrubbing mist, and is removed in the condensate. The scrubber 

shall be designed to remove a minimum of 99 percent of hydrogen sulfide in the foul 

stream. Acceptable chemical scrubber manufacturers are Calvert Environmental Co., 

San Diego, CA, and Quad Environmental Technologies, Corp., Highland Park, IL. 

All odor control and ventilation equipment shall be suitable for continuous exposure 

to saturated hydrogen sulfide gas, sodium hypochlorite mist, sodium hydroxide mist 

and sulfuric acid. Electrical equipment shall have explosion proof enclosure designed 

for hazardous condition for Class 1, Division 1, locations. 

For air pollution permits, consult South Coast Air Quality Management District. 

D. Dry Well Ventilation 

The pump station dry well is normally located adjacent to the wet well to house the 

pumps, valves, meters and other ancillary equipment. 

The dry well and equipment rooms shall be designed for a ventilation rate of at least 

15 air changes per hour or ventilation rate equivalent to cool internal heat load from 




the equipment whichever is greater or not greater than 60 air changes per hour. The 

sensible cooling ventilation rate shall be calculated as follows: 

where: 

H = cfm x 1.09 x t 

H = Internal heat gain from equipment, Btu per hour 

cfm = Air flow, cu ft per minute 

t = Change in internal temperature, degree F. Use 10 degrees F for change 

in internal temperature as adequate for sensible cooling. 

Where a pump station is equipped with variable frequency drives (VFD), the VFD 

shall be installed in an air conditioned room with 90 percent efficient outside air 

filters. VFD units are inherently sensitive to temperature, dust, moisture and other 

corrosive elements in the air. For constant speed pump stations, the motor control 

center (MCC) and control rooms shall be equipped with a ventilation fan and 90 

percent efficient outside air filters. Pump and equipment room air inlets shall be 

provided with 30 percent efficient outside air filters. All air filters shall be provided 

with differential pressure gages to indicate when the filters are clogged, and flow 

detection devices connected to alarm signaling systems to indicate ventilation 

system failure. 

E. Fire Protection System 

Where required by NFPA or by the Fire Department, necessary fire protection 

systems shall be provided in required areas. For areas housing electrical equipment 

such as the motor control centers, computer rooms and control rooms, an approved 

type fire protection systems shall be provided. 

F. Gas Detection System 

Combustible gas detection equipment shall be provided in the wet well and dry well, 

and other areas where hazardous gas may be present, to record, activate alarms 

and/or to operate the ventilation system. The stationary gas detection system shall 

be capable of measuring concentrations of hydrogen sulfide, methane gas and/or 

petroleum vapor in the air. 

The combustible gas sensor shall be DET-TRONICS Point Watch Infrared 

Hydrocarbon Gas Detector Model PIR9400 or approved equal. The sensor shall be 

mounted in the wet well such that it can be removable externally for maintenance 

and calibration. It shall be connected to the programmable logic controller (PLC). 

The PLC shall monitor the combustible gas sensor through the 4-20 mA signal which 

shall be proportional to combustible gas concentrations of zero to 100%. Two (2) 

PLC adjustable alarms shall be provided. 6% lower explosion level (LEL) shall 

indicate a warning, and 10% LEL shall indicate an alarm. Alarm beacons shall be 

installed in the dry well and the electrical room. 

An entry control station shall be provided in a NEMA 4X stainless steel enclosure 

with vandal resistant hardware, and amber and green NEMA 4 vandal resistant pilot 

lights at or near each entry. They shall indicate a potentially dangerous condition in 




the pump station based on the loss of the ventilation system, combustible gas, loss 

of positive pressure in the electrical room, or loss of negative pressure in the dry 

well. Both lights shall be dark if there is a component or power failure. A lamp test 

switch shall be provided, which will activate all entry control system lights for ten 

seconds for testing. 

G. Compressed Air System 

For pump stations using surge tanks, air operated valves; pneumatic tools for 

maintenance purposes, and instrument air, a compressed air system shall be 

provided. The air system for pneumatic tools shall consist of a lubricated type air 

compressor, receivers, air dryers and necessary piping system. For an instrument 

air system, a dedicated non-lubricated type air compressor, receiver, dryer and 

necessary piping system shall be provided. Where the valve operators are designed 

as pump control valves with the option to have controlled closing during power 

failure, the air receivers shall be sized to store compressed air capable of stroking 

the air cylinders three (3) complete cycles between the specified operating pressures 

during power outages. 

H. Hydraulic System 

Pump stations equipped with hydraulic operated valves shall be provided with 

hydraulic systems. The hydraulic system shall be either a package system supplied 

with each valve, or one complete package to operate multiple valves. The system 

shall consist of an oil reservoir, hydraulic pumps, control valves, hydraulic cylinders, 

limit switches and nitrogen gas-filled accumulators where the valves are required to 

operate during power outages. The valve opening and closing ranges shall be 

specified. Final field adjustments shall be made during pump station start-up. 

I. Noise Control 

The pump station shall be designed to meet the minimum noise level requirement of 

the Municipal Code of the local jurisdictional agency and the Occupational Safety 

and Health Administration (CAL/OSHA). All mechanical equipment and enclosures 

shall be acoustically treated to bring the noise level down to an acceptable limit. 

These attenuation devices may consist of exhaust mufflers, sound isolators or 

acoustical panels. 

The pump stations shall be designed with noise levels not more than 5 dBA above 

the ambient noise level as measured at the property line of the nearest recipient 

(neighbor). A 24 hour noise level reading shall be measured at the pump station site 

as basis of the design. 

In the absence of actual field measurements, the presumed ambient noise level shall 

be deemed to be the minimum ambient noise level for each zone as follows: 

Sound Level “A”Decibels 

(In this chart, daytime levels are to be used from 7:00 A.M. to 10:00 P.M. and 

nighttime levels from 10:00 P.M. to 7:00 A.M.) 




Presumed Ambient Noise Level (dBA) 

Zone Day Night 

Residential 50 40 

Public Facility, Commercial, Recreational 60 55 

Industrial 65 65 

At the boundary line between two zones, the presumed ambient noise level of the 

quieter zone shall be used. 

J. Sump Pumps 

A sump pit shall be provided in all underground structures such as dry wells, valve 

and electrical vaults. The sump pit shall be equipped with an adequately sized plus a 

standby unit, each having a minimum capacity of 50 gpm. Submersible sump pumps 

shall be used and controlled by a duplex type control, an automatic alternator and a 

float switch level control. The control system shall be designed to start the standby 

pump when the lead pump fails to start or when the water level continues to rise 

while the lead pump is operating. Both pumps are to stop at low water level. 

Sump pump discharge pipe, fittings and valves shall be Schedule 80 PVC pipe, with 

minimum diameter of 2-inches. Each sump pump discharge pipe shall be provided 

with a swing check valve and isolation gate valve mounted above, both in the vertical 

position. A common discharge manifold shall terminate inside the wet well with the 

wall penetration above the highest surcharge elevation of the wet well. 

K. Spare Parts 

Pump station electro-mechanical equipment shall be provided with spare parts 

necessary to ensure continuous operation. The recommended spare parts shall be 

determined by the project design engineer with assistance from the City Engineer. 

The following shall be the minimum list of spare parts: 

1. One set of pump and motor bearings for each size and model of pump unit. 

2. One set of pump seals for each size and model of pump unit. 

3. One set of pump and casing wear rings for each size and model of pump unit. 

4. One set of pump and motor for each size and model of pumping unit. 

5. One dozen fuses for each size of fuse. 

6. A printed circuit board for each size and model of the variable frequency 

drives. 

The spare parts shall be delivered to the project site no later than two (2) months 

prior to pump station start up. Spare parts required during testing and start-up shall 

be provided by the contractor. 




17.14 Electrical Equipment 

Electrical systems in the pump station consist of the power supply, power transformers, 

motor control centers, electric motors, electric variable speed drives, electrical wires and 

conduits, lighting fixtures, and other associated interface with the instrumentation and 

control systems. 

A. Power Supply 

The standard power supply to the pump station shall be 480 volts. 

B. Motor Control Centers (MCC) 

All motor starters and disconnect switches shall be installed in NEMA 3R Motor 

Control Centers (MCC). MCC rooms shall be located away from hazardous gas or 

other corrosive environments. Mechanical ventilation equipment shall be provided to 

maintain air circulation. All fresh air inlets to the MCC rooms shall be provided with 

90 percent efficient inlet filters. 

Where environmental problems exist in the pump station location, such as the 

presence of dust, moisture from sea water, or corrosive gas, the MCC room shall be 

designed to have adequate ventilation and provided with air cleaning equipment 

such as de-humidifiers, filters or carbon absorbers. 

The MCC circuit breaker handles must be provided with safety interlocks. 

C. Electrical Cables and Conduits 

All electrical cables and conduits shall be designed in accordance with the NEMA 

Area Classification as required by the service area. All electrical conduits shall be 

PVC coated galvanized rigid metallic conduits or Schedule 80 PVC. All conduits 

shall be sized for 100 year service. Spare conduits may be required. The minimum 

size conduit shall be 1-inch. 

17.15 Instrumentation and Controls 

The instrumentation and control system shall be designed to operate the pump station to 

match the flow characteristics of the service area. The control system shall consist of the 

wet well level control, flow metering equipment, pressure gages and switches, fire alarms 

and gas detection instruments. 

A. Pump Control System 

1. General 

The pump control panel (PCP) provides manual or automatic control of the 

pumps, as well as visual indication of the pump station status and alarm 

conditions. The following status and alarm indicators are to be provided as a 

minimum: 




Status 

Power ON Light 

Running Time Meter 

Pump RUN 

HAND-OFF-AUTO selector switch 

Lights Test Pushbutton 

Seal Test Pushbutton (for submersible pumps) 

Flow Rate Indicator 

Wet Well Level Indicator 

Discharge Pressure Indicators 

Alarms 

Wet Well HIGH LEVEL Alarm Light (from 

Ultrasonic) 

Wet Well High High Level Alarm Light 

Pump FAIL Alarm Light 

Motor winding HIGH TEMP Alarm Light 

Seal FAIL Alarm Light (for submersible 

pumps) 

FAIL RESET pushbutton 

The pump(s) may be controlled either manually, or automatically, depending 

upon the position of the pump hand-off-auto selector switch. In the MANUAL 

mode, a pump is started by placing its hand-off-auto selector switch in the 

HAND position. In this mode, the pump will run continuously unless shut 

down by the “fail”interlocks. 

In the AUTO mode, the pump is started and stopped by the wet well level, as 

measured by an ultrasonic level sensor. In the “Auto”mode, the pump will 

run until called to stop by wet well level, unless shut down by the “fail” 

interlocks. 

In the AUTO mode, the pumps will alternate operation automatically after 

each pump down cycle. If the operating pump should fail, the next pump in 

the call sequence will start and operate each time the wet well level calls for a 

pump operation until the failed condition is cleared. 

The pump controller shall be a solid state device, which provides operational 

set points, high level alarm, outputs to start and stop the pumps, and perform 

pump alternation. The controller shall be a U.S. Filter D153U triplex 

controller/alternator or approved equal. 

Float switches shall be installed in the wet well to provide an emergency high 

level alarm and a back up pump control system for the station. The 

emergency high level is to be indicated on the pump control panel and 

through the dialer. In this condition, the pump will operate for an adjustable 

time (0-5 minutes after emergency high level initiation), as set by the 

operator, and then will shut down. If the wet well level again rises to the 

emergency high level, the cycle will be repeated. The station can run 

indefinitely in this mode if necessary. 

A “pump fail”alarm (for each pump) will be indicated at the pump control 

panel and transmitted to the automatic dialer system should any of the 

following conditions occur: 

• Pump motor winding high temperature detected by sensors in the motor 

winding. 

• Motor overload detected by the overload relay. 




Each of the above “fail”conditions will lock-out the pump from operation. To 

reset a pump, the operator must visit the station, determine the cause of 

failure, correct the condition, and depress the “fail reset”pushbutton on the 

pump control panel. 

For submersible pumps, a motor seal failure will also be detected and 

alarmed but will not stop pump operation. 

2. Constant Speed Pump Control System 

The operating sequence is applicable for multiple pump units installed in a 

smaller wet well. The pump station will start in sequence, pumps start and 

stop in the reverse order. 

This sequence is recommended for the following reasons: 

a. To maintain uniform flow into the receiving system 

b. To provide smaller wet well storage volume and less number of motor 

starts per hour; 

c. To reduce sewer gas emission to the atmosphere by maintaining a 

constant water level in the wet well. 

3. Variable Speed Drives. 

Variable speed (matched-flow) pumps shall be used for the following 

conditions; 

a. Where more uniform discharge to the receiving system is required; 

b. Where there is not enough space in the pump station to 

accommodate installation of multiple smaller unit constant speed 

pumps; 

c. Where the wet well volume is limited to satisfy maximum starts per 

hour; 

d. Where sewer gas emissions to the atmosphere should be limited; 

The minimum force main velocity requirements will not be violated due 

to operation with variable frequency drives. 

The variable speed drive pumps shall be controlled as follows: 

a. When the wet well level reaches the first set level, the lead pump will 

start and ramp to a minimum preset speed. As the flow increases, the 

pump speed will increase in proportion to the increase in flow in order 

to maintain the level in the wet well until the pump has reached its 

maximum speed. 




. When the inflow to the wet well exceeds the maximum capacity of the 

lead pump, the control system will then start the lag pump. The lag 

pump will increase its speed while the lead pump will decrease its 

speed up to the point where the two pumps share the flow, both at the 

same speed. As the inflow increases, the two pumps will increase 

their speeds in proportion to the inflow until the pumps have reached 

the maximum pump design flow, in the case of two pump 

combination. 

c. A drop in wet well level equivalent to a decrease in pump station 

inflow will signal the pumps to slow down until a preset speed is 

reached. Then the lag pump will stop, and the lead pump will increase 

its speed in proportion to the inflow. 

d. Further drop in wet well level will signal the lead pump to slow down 

until the minimum level is reached, at which level, the lead pump will 

stop. 

e. In the event that either the lead pump or the lag pump fails, the wet 

well level will rise and the standby pump will be started at the same 

time the failure alarm is activated. The standby pump will be provided 

with a variable speed drive. 

For pump stations equipped with more than two variable speed pumps, the 

same operating sequence will be followed. 

Under no conditions will a force main velocity of less than 3 feet per second 

shall be allowed. 

The variable speed drives shall be provided with bypass contactors to 

operate the pump at full speed when the VFD is not available. 

4. Float Level Switch 

The float level switches shall be used to detect the low-low level cut-off and 

the high-high water level alarm, and as an auxiliary system in the event of 

failure of the ultrasonic level control systems. When the water level in the wet 

well reaches the high-high level, the control system (US Filter CBIT B300 

single stage controller or approved equal) shall initiate a timed pump down 

using all pumps. The pump station shall be capable of operating indefinitely 

in this mode. The float switch shall be direct acting with a single pole 

mercury switch which activates when the longitudinal axis of the float is 

horizontal and de-actuates when the liquid level falls 1-inch below the 

actuation level. The switch shall be encapsulated in a chemical resistant 

polypropylene casing with a firmly bonded electrical cable protruding. The 

entire assembly shall be watertight and impact resistant designed and 

manufactured for Class 1 Division 1, Hazardous Conditions. Float switches 

shall be Roto-Float as manufactured by Anchor Scientific or approved equal. 




Submersible dewatering sump pumps located in dry wells and valve 

structures shall be controlled by float switches. Float switches shall be 

designed and manufactured suitable for the area classification of the sump 

pit. 

5. Ultrasonic Level Control 

The pump station’s primary level controller shall be the ultrasonic level 

sensor. The transducers shall be hermetically sealed, self cleaning with builtin 

temperature compensation 6 o beam angle, suitable for installation in a 

sewage pump station wet well. 

Ultrasonic measuring systems shall be the Hydroranger with XPS-15 

transducer as manufactured by Milltronics, or approved equal. 

17.16 Supervisory Control and Data Acquisition (SCADA) System 

To monitor and control the operation of the pump station remotely at a central station, 

SCADA system equipment shall be provided. The system shall consist of the Remote 

Telemetry Unit (RTU) located in the pump station connected to a computer at a designated 

central station. The signal to the central station shall be transmitted over spread spectrum 

radio. 

The pump operation is initiated by a motor starter mounted in the Motor Control Center 

(MCC). The starter is controlled by a signal from the level sensor or push buttons or by local 

control automation, such as the remote telemetry unit. 

The Central Computer System displays information such as graphics and tables; gathers 

historical data such as trends of pumping cycles, measurement of flows and pressures, 

equipment running time, number of pump starts per hour; and can remotely control the 

operation of the pump stations. 

17.17 Pressure Gauges 

In a wet well-dry well type pump station, pressure gauges shall be installed at the suction 

and discharge sides of each pump to measure the pump total dynamic head. The pressure 

gauges shall be at least 4-1/2 inches in diameter. Where seal flushing water is required, a 

pressure gauge and low pressure switch shall be provided to activate an alarm in case of 

loss of flushing water. A low flow alarm switch may be used in lieu of the pressure switch. 

A pressure switch shall be provided between the pump and the check valve or pump control 

valve to activate an alarm in the event of failure of the valve to open or accidental closure of 

any isolation valve located at the pump discharge piping. A micro-switch attached to the 

valve shaft may be provided in lieu of the pressure switch. 

All, pressure gauges and switches installed in a piping system carrying solids bearing fluids 

such as wastewater, sump pump discharge or chemical lines shall be provided with 

diaphragm seals and snubbers where pulsating flow is expected. The assembly shall be 

provided with an isolation ball valve for maintenance. Diaphragm seal material shall be 

compatible with the pressure and fluid being handled. 




In a submersible pump station, a pressure gauge/switch shall be installed in the discharge 

pipe of each pump in the valve vault upstream of the check valve. The discharge pressures 

shall be indicated in the pump control panel. 

17.18 Pump Station Facility 

The pump station facility includes the pump station structure, buildings, electrical substation 

or transformer, access roads and other appurtenant equipment inside the property. The 

facility design shall incorporate access road and security. The architectural treatment shall 

blend with the surrounding area. 

A. Building Design and Materials of Construction 

17.19 Force Mains 

The pump station usually consists of an underground concrete structure to house the 

wet well and the dry well. Where the pump station requires an above ground 

structure to house the electrical room, generator room, office area and maintenance 

shop, the above ground building shall be designed in accordance with the 

requirements of the Uniform Building Code and California Fire Code. In general, all 

buildings shall be cast-in-place concrete or masonry block wall construction. 

Wet Well and Dry Well. The wet well and dry well shall be reinforced cast-in-place 

concrete with wall thickness to withstand the earth and seismic loads, and shall be 

heavy enough to resist floatation without earth skin friction resisting the outside 

surfaces when the wet well is empty. 

The size and configuration of the wet well shall be designed in accordance with 

Section 17.5. The bottom of the wet well shall be sloped to at least 15 degrees and 

corners grouted to prevent accumulation of solids during operation. 

The dry well shall be designed to provide the following: 

1. Minimum of 42-inch clear working clearance between pumps and piping; 

2. Access doors, stairways and landing; 

3. Access opening for equipment installation, maintenance and removal; 

4. Hoisting equipment or lifting hooks; 

5. Adequate ventilation 

6 Fire protection equipment where required. 

The minimum diameter for a force main shall be 4 inches. The capacity of the force main 

shall be the design peak flow from the pump station. The minimum design velocity for a 

force main shall be 3.0 fps, and maximum allowed 5.0 fps for PVC and 6.0 fps for ceramic 

epoxy lined DIP. 




Force mains shall continuously rise from the pump station to the terminal manhole to 

eliminate the need for air and vacuum release valves. 

For new pump stations with phased development of the tributary area, dual force mains may 

be required. The City Engineer shall select the number of force mains that will be installed 

at each pump station. 

17.20 Access Roads 

Pump stations shall be designed with access roads for construction, operation and 

maintenance of the equipment. The roads shall have turning radii suitable for the size of 

vehicle, or heavy hoisting equipment necessary for installation, removal or delivery of 

equipment or supplies into the station. Pavement sections shall be able to support the load 

of the heaviest anticipated equipment to be used in the station. Where monorail hoists or 

traveling cranes are required, adequate headroom clearance shall be provided or loading 

docks can be used to limit the height of the building. 

17.21 Flood Control 

The pump stations shall be designed with pad elevation one foot above the expected 

value100-year flood elevation or the elevations indicated on the Flood Insurance Rate Maps 

in areas where detailed studies have been conducted, whichever is higher. Where available 

and current, information contained in the Orange County Public Facilities and Resources 

Department documents can be used to determine the expected value 100-year flood 

elevation. 

All hydrologic and hydraulic calculations and design shall be in accordance with the 

standards of the jurisdictional flood control agency standards. 

17.22 Grading and Area Drainage 

The site drainage shall be designed to prevent standing water or the erosive effects of storm 

runoff. Pavement areas shall have a positive drain of up to 3%. Flow lines shall have a 

minimum of 1% slope. Underground structures shall not be constructed in partially cut and 

partially fill. Where this condition exists, the site shall be over-excavated and re-stabilized. 

The pump station shall be designed not to float where high groundwater exists. 

17.23 Soils Report 

A geotechnical investigation shall be conducted to determine the underground soils 

conditions. The Soils report shall show the foundation design criteria, corrosiveness of soils 

and ground water, groundwater elevations if it exists, and possible hazardous materials 

underground. Cleaning of such materials shall be addressed in the construction contract, or 

can be awarded to a separate hazardous materials contractor as determined by the City 

Engineer. 

17.24 Surveying 

The control bench marks shall be referenced from the County of Orange records. Where 

existing survey and reference plans are available, field check existing data with the current 




datum and adjust all elevations to current datum where required.. The location of the pump 

station shall be tied to a nearby street and to an existing property line. Basis of survey 

bearings and control shall be given if the local coordinate are established. 

17.25 Security 

The pump station site shall be provided with an 8 foot high chain link fence or masonry block 

wall fence, as directed by the City Engineer. The fence or wall shall be designed in 

accordance with applicable American Public Works Association Standards. The entrance 

gate shall be secured with a padlock. Where the pump station has a superstructure housing 

the motor control center and the generator, the building shall be equipped with intrusion 

alarms. Where there is no superstructure, the NEMA 3R enclosure housing the motor 

control center shall be equipped with an intrusion alarm. The alarms shall be connected to a 

horn mounted in the building, a red beacon light mounted outside the building or above the 

NEMA 3R enclosure, and remoted via telemetry to the main control system. 

17.26 Water Supply System 

The pump station water supply system shall be provided for pump seal water system, 

irrigation system, rest rooms and housekeeping hose downs. A backflow preventer shall be 

installed in the pipeline connecting the hose bibs, seal water and irrigation system. Seal 

water systems shall utilize air gap tanks, and not be directly connected to the water supply 

system. All piping shall be designed in conformance with the Uniform Plumbing Code. 

17.27 Landscaping and Irrigation System 

Plants selected shall be drought resistant and approved by the City Engineer. Irrigation 

system equipment shall utilize water saving kits that are controlled by automatic timers. 

17.28 Construction 

The pump station shall be constructed in conformance with the specifications and drawings. 

The pump station construction shall be administered and inspected by the City of Norwalk, 

or its designated representative. 

A. Shop Drawing Submittal and Shop Drawing Review 

The Technical Specifications shall specify the requirements for shop drawing 

submittal and review process. 

Once the project is awarded, shop drawing submittals shall be reviewed and 

accepted. The shop drawing review is one way to check compliance with the 

specifications. It also serves as a mechanism to get from the contractor the 

equipment as specified. Where a substitution to specified equipment is proposed to 

the construction project Design Engineer for review, the design project engineer shall 

be consulted. 




B. Equipment Installation and Testing 

The equipment installation and testing shall be specified in each equipment 

specification. Normally, the equipment shall be specified to be installed by the 

Contractor under the supervision of a certified factory representative. After 

installation, the Contractor shall conduct trial operation of the equipment, and make 

the necessary adjustments as required. When the equipment becomes operational, 

the Contractor shall test the equipment in the presence of the City’s representative. 

The test shall include a performance test, simulating the manual and automatic 

operation, and checking of other components in compliance with the specifications. 

The test shall also include verification of all alarm functions. A continuous test using 

the actual process material shall be conducted without any Norwalkkdown prior to 

final acceptance. 

C. Operation and Maintenance Manuals 

The Operation and Maintenance Manual shall be prepared by the construction 

contractor based upon the plans and specifications, and assistance from equipment 

manufacturers, to clearly describe how the pump station shall operate under normal 

and emergency conditions, and how it should be maintained. 

Final payment shall not be made to the Contractor until the Operation and 

Maintenance Manual is approved by the City Engineer. 

D. Operator Training 

Each pump station has unique operational requirements and some have equipment 

that requires familiarization by the station operators. The Contractor shall provide 

training, through respective authorized equipment representatives, to the station 

operators as specified in the Contract Documents. 

18. INSPECTION AND TESTING OF GRAVITY SEWERS 

18.01 CCTV Inspection 

The Contractor shall perform Closed Circuit Television inspection (CCTV) of all gravity 

sewers to determine alignment, grade and damaged or defective pipe in place; after the pipe 

has been installed, backfilled and compacted to grade, tested for leakage, manholes raised 

to grade, but prior to final resurfacing, from manhole to manhole. CCTV inspection shall be 

recorded on DVD, and recording procedures shall conform to the requirements of Standard 

Specifications for Public Works Construction Section 500-1.1.5, Television Inspection, 

except that the maximum speed shall be 15 feet per minute. The recording shall 

continuously display the following on-screen data: contract number, project name, date, 

time, distance (in feet) from the insertion manhole, and manhole identification codes. 

Two copies of the recording shall be submitted to the City for approval within two days of the 

CCTV inspection. CCTV recording shall be performed first with the pipe dry, and then 

immediately following clean water flowing in the pipe to clearly indicate vertical 

misalignments, sags or other defects. Should CCTV inspection indicate any faulty 

installation of the pipe, repairs or replacement shall be made at the Contractor’s expense by 




a method approved by the City. Repaired and or replaced pipe and/or segments shall be 

retested and reinspected through CCTV at no additional cost to the City, until final 

acceptance is granted. Any sag greater than one (1) 0.25 inch in 100 feet of pipe reach 

shall be considered excessive, and the pipe shall be removed and reinstalled to proper 

grade. 

18.02 Gravity Pipe Leakage Tests 

All gravity sewer pipes and service laterals shall be tested for exfiltration and/or infiltration 

and deflection. All leakage tests shall be in conformance with Standard Specifications for 

Public Works Construction (SSPWC), “GREENBOOK" Section 306-1.4.1. Water exfiltration 

test shall be in conformance with SSPWC Section 306-1-4.2. Air pressure test shall be in 

conformance with SSPWC 306-1.4.4. All testing shall be performed in the presence of the 

City Inspector. 

18.03 Manhole Leakage Tests 

1. Leakage tests shall be made and observed by the City Inspector on each manhole. 

The test shall be the exfiltration test made as described below: 

2. After the manhole has been assembled in place, all lifting holes and those exterior 

joints within 6 feet of the ground surface shall be filled and pointed with an approved 

non-shrinking mortar and the lining joints completed. The test shall be made prior to 

placing the shelf and invert. If the groundwater table has been allowed to rise above 

the bottom of the manhole, it shall be lowered for the duration of the test. All pipes 

and other openings into the manhole shall be suitably plugged and the plugs braced 

to prevent blow out. 

3. The manhole shall then be filled with water to the top of the cone section. If the 

excavation has not been backfilled and observation indicates no visible leakage, that 

is, no water visibly moving down the surface of the manhole, the manhole may be 

considered to be satisfactorily water-tight. If the test, as described above is 

unsatisfactory as determined by the City Inspector, or if the manhole excavation has 

been backfilled, the test shall be continued. A period of time may be permitted if the 

Contractor so wishes, to allow for absorption. At the end of this period, the manhole 

shall be refilled at the top of the cone, if necessary and the measuring time of at least 

8 hours begun. At the end of the test period, the manhole shall be refilled to the top 

of the cone, measuring the volume of water added. This amount shall be 

extrapolated to a 24-hour rate and the leakage determined on the basis of depth. 

The leakage for each manhole shall not exceed 1 gallon per vertical foot for a 24- 

hour period. If the manhole fails this requirement, but the leakage does not exceed 

3 gallons per vertical foot per day, repairs by approved methods may be made as 

directed by the City to bring the leakage within the allowable rate of 1 gallon per foot 

per day. Leakage due to a defective section or joint or exceeding the 3 gallon per 

vertical foot per day shall be the cause for the rejection of the manhole. It shall be 

the Contractor’s responsibility to uncover the manhole as necessary and to 

disassemble, reconstruct or replace it as directed by the City Engineer. The 

manhole shall then be retested and, if satisfactory, interior joints shall be filled and 

pointed. 




4. No adjustment in the leakage allowance will be made for unknown causes such as 

leaking plugs, absorptions, etc., i.e., it will be assumed that all loss of water during 

the test is a result of leaks through the joints or through the concrete. Furthermore, 

the Contractor shall take all steps necessary to assure the City Inspector that the 

water table is below the bottom of the manhole throughout the test. 

5. If the groundwater table is above the highest joint in the manhole, and if there is no 

leakage into the manhole as determined by the Engineer, such a test can be used to 

evaluate the water-tightness of the manhole. However, if the City Engineer is not 

satisfied, the Contractor shall lower the water table and carry out the test as 

described herein before. 

18.04 Pipe Slope 

All gravity sewer pipe shall be laid to the line and grade shown on the plans and per Section 

306.1.2 of “GREENBOOK,”with a maximum allowable tolerance of 0.125 inch at the invert. 

The Contractor shall continuously check the grade of the pipe being installed through the 

use of laser line. 

19. STANDARD SEWER NOTES 

The following notes must appear on the plans under Standard Sewer Notes. 

A. The sewer Contractor shall have a copy of the Project Plans and Specifications, as 

well as the City of Norwalk Design Standards for Sewer Facilities on the job site. 

B. The Contractor shall obtain a City and/or County permit for work done on public 

right-of-way. 

C. The City of Norwalk Engineering Office shall be called for inspection five (5) working 

days before start of work at (562) 929-5723. 

D. A pre-construction conference shall be held 48 hours before starting construction 

work. 

E. The Contractor shall expose all join points to the existing sewer system for 

verification of location and elevation before construction. 

F. Stations shown as 1+00.00 are sewer stations and are independent of all other 

stations. 

G. All laterals shall be staked by a surveyor before trenching and a complete set of cut 

sheets shall be supplied to the Contractor and the City Inspector. 

H. The City will inspect and test the sewer collection system and lateral sewers to the 

property clean-out. Privately owned sewer laterals from the property line clean-out 

will be inspected and tested by an approved contractor subject to the City of Norwalk 

Building Department approval. 

J. All sewer lines shall be balled in the presence of the City Inspector before 

completion of all leakage tests. 




K. Pipeline leakage tests shall be made in the presence of the City Inspector, only after 

backfill has been completed, compaction tests on backfill have been made, and the 

backfill has been accepted by the City Inspector. 

L. All sewer main lines shall be inspected using a closed circuit television system. Two 

recordings shall be made of the inspection on a DVD disk in accordance with 

Subsection 18.1 of the City of Norwalk Design Standards for Sewer Facilities. One 

recording shall inspect the system constructed with no flow, and one shall conduct 

the inspection 15 minutes after flowing water in the sewer. 

M. The Contractor shall provide the City of Norwalk with an as-built set of job prints with 

tie-down measurements for all laterals and manholes. 

N. Before final acceptance, the developer’s engineer signing the plans shall furnish the 

City of Norwalk with a set of as-built mylars of the sewer plan. 

O. Curbs or pavement surfaces in alleys where sewer laterals exist shall be inscribed 

with an “S”indicating locations of all sewer laterals. 

P. Curbs shall be inscribed with ties for all manhole locations. 

Add the following notes to plans having on-site work which will be dedicated to the 

City: 

Q. Trench backfill, on all sewer lines to be dedicated to the City, shall be compacted to 

a minimum of 90% relative density as determined by the five-layer test method 

(California 216G). Tests will be required every 300-feet of trench or as determined 

by the City Inspector. The developer shall submit written results of compaction 

testing to the City before acceptance. If in a dedicated street or a future street, 

compaction will be as required by governmental agency having jurisdiction, but no 

less than 90 percent relative compaction.

Design and Performance Provisions - City of Norwalk

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